Therapeutic RNA interference of malignant melanoma by electrotransfer of small interfering RNA targeting Mitf

New insights into the mechanism of electrotransfer of small nucleic acids

RNA interference (RNAi) is a powerful and rapidly developing technology that enables precise silencing of genes of interest. However, the clinical development of RNAi is hampered by the limited cellular uptake and stability of the transferred molecules. Electroporation (EP) is an efficient and versatile technique for the transfer of both RNA and DNA. Although the mechanism of electrotransfer of small nucleic acids has been studied previously, too little is known about the potential effects of significantly larger pDNA on this process. Here we present a fundamental study of the mechanism of electrotransfer of oligonucleotides and siRNA that occur independently and simultaneously with pDNA by employing confocal fluorescence microscopy. In contrast to the conditional understanding of the mechanism, we have shown that the electrotransfer of oligonucleotides and siRNA is driven by both electrophoretic forces and diffusion after EP, followed by subsequent entry into the nucleus within 5 min after treatment. The study also revealed that the efficiency of siRNA electrotransfer decreases in response to an increase in pDNA concentration. Overall, the study provides new insights into the mechanism of electrotransfer of small nucleic acids which may have broader implications for the future application of RNAi-based strategies.

Upregulation of the novel lncRNA U731166 is associated with migration, invasion and vemurafenib resistance in melanoma

Our previous work using a melanoma progression model composed of melanocytic cells (melanocytes, primary and metastatic melanoma samples) demonstrated various deregulated genes, including a few known lncRNAs. Further analysis was conducted to discover novel lncRNAs associated with melanoma, and candidates were prioritized for their potential association with invasiveness or other metastasis‐related processes. In this sense, we found the intergenic lncRNA U73166 (ENSG00000230454) and decided to explore its effects in melanoma. For that, we silenced the lncRNA U73166 expression using shRNAs in a melanoma cell line. Next, we experimentally investigated its functions and found that migration and invasion had significantly decreased in knockdown cells, indicating an essential association of lncRNA U73166 for cancer processes. Additionally, using naïve and vemurafenib‐resistant cell lines and data from a patient before and after resistance, we found that vemurafenib‐resistant samples had a higher expression of lncRNA U73166. Also, we retrieved data from the literature that indicates lncRNA U73166 may act as a mediator of RNA processing and cell invasion, probably inducing a more aggressive phenotype. Therefore, our results suggest a relevant role of lncRNA U73166 in metastasis development. We also pointed herein the lncRNA U73166 as a new possible biomarker or target to help overcome clinical vemurafenib resistance.

Use of Nanoparticles in Delivery of Nucleic Acids for Melanoma Treatment

Melanoma accounts for 4% of all skin cancer malignancies, with only 14% of diagnosed patients surviving for more than 5 years after diagnosis. Until now, there is no clear understanding of the detailed molecular contributors of melanoma pathogenesis. Accordingly, more research is needed to understand melanoma development and prognosis.All the treatment approaches that are currently applied have several significant limitations that prevent effective use in melanoma. One major limitation in the treatment of cancer is the acquisition of multidrug resistance (MDR). The MDR results in significant treatment failure and poor clinical outcomes in several cancers, including skin cancer. Treatment of melanoma is especially retarded by MDR. Despite the current advances in targeted and immune-mediated therapy, treatment arms of melanoma are severely limited and stand as a significant clinical challenge. Further, the poor pharmacokinetic profile of currently used chemotherapeutic agents is another reason for treatment failure. Therefore, more research is needed to develop novel drugs and carrier tools for more effective and targeted treatment.Nucleic acid therapy is based on nucleic acids or chemical compounds that are closely related, such as antisense oligonucleotides, aptamers, and small-interfering RNAs that are usually used in situations when a specific gene implicated in a disorder is deemed a therapeutically beneficial target for inhibition. However, the proper application for nucleic acid therapies is hampered by the development of an effective delivery system that can maintain their stability in the systemic circulation and enhance their uptake by the target cells. In this chapter, the prognosis of the different types of melanoma along with the currently used medications is highlighted, and the different types of nucleic acids along with the currently available nanoparticle systems for delivering these nucleic acids into melanoma cells are discussed. We also discuss recently conducted research on the use of different types of nanoparticles for nucleic acid delivery into melanoma cells and highlight the most significant outcomes.

Skin Delivery of siRNA Using Sponge Spicules in Combination with Cationic Flexible Liposomes

We report the topical administration of sponge Haliclona sp. Spicules (SHS) combined with cationic flexible liposomes (CFL) to increase the delivery of small interfering RNA (siRNA) into viable skin cells in vitro and in vivo. SHS can be applied topically as novel microneedles to overcome skin barrier by creating plenty of new microchannels in stratum corneum. Subsequently, well-designed CFL can be also utilized topically as nanocarriers to overcome skin cells membrane by delivering siRNA to skin deep layers through these microchannels and thereby facilitating their cell internalization. The topical application of SHS in combination with CFL (0.05% of lipids, w/v), referred to as CFL(0.05%), enhanced siRNA skin penetration in vitro by 72.95 ± 2.97-fold compared to control group (p < 0.001). Further, the topical application of SHS in combination with CFL(0.05%) on female BALB/c mice skin resulted in 29.21% ± 1.41% of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) knockdown at all application area in vivo, which was not significantly different from the GAPDH protein knockdown rate in the subcutaneous injection center. However, the high knockdown rate only appears in the vicinity (<0.5 cm) of the injection center. In sum, this study provides a promising strategy of topical delivery of siRNA by the combined used of SHS and well-designed CFL.

Resistance to ursolic acid-induced apoptosis through involvement of melanogenesis and COX-2/PGE2 pathways in human M4Beu melanoma cancer cells

Melanoma is one of the most aggressive forms of cancer with a continuously growing incidence worldwide and is usually resistant to chemotherapy agents, which is due in part to a strong resistance to apoptosis. Previously, we had showed that B16-F0 murine melanoma cells undergoing apoptosis are able to delay their own death induced by ursolic acid (UA), a natural pentacyclic triterpenoid compound. We had demonstrated that tyrosinase and TRP-1 up-regulation in apoptotic cells and the subsequent production of melanin were implicated in an apoptosis resistance mechanism. Several resistance mechanisms to apoptosis have been characterized in melanoma such as hyperactivation of DNA repair mechanisms, drug efflux systems, and reinforcement of survival signals (PI3K/Akt, NF-κB and Raf/MAPK pathways). Otherwise, other mechanisms of apoptosis resistance involving different proteins, such as cyclooxygenase-2 (COX-2), have been described in many cancer types. By using a strategy of specific inhibition of each ways, we suggested that there was an interaction between melanogenesis and COX-2/PGE2 pathway. This was characterized by analyzing the COX-2 expression and activity, the expression of tyrosinase and melanin production. Furthermore, we showed that anti-proliferative and proapoptotic effects of UA were mediated through modulation of multiple signaling pathways including Akt and ERK-1/2 proteins. Our study not only uncovers underlying molecular mechanisms of UA action in human melanoma cancer cells but also suggest its great potential as an adjuvant in treatment and cancer prevention.

Transdermal Delivery of siRNA through Microneedle Array

Successful development of siRNA therapies has significant potential for the treatment of skin conditions (alopecia, allergic skin diseases, hyperpigmentation, psoriasis, skin cancer, pachyonychia congenital) caused by aberrant gene expression. Although hypodermic needles can be used to effectively deliver siRNA through the stratum corneum, the major challenge is that this approach is painful and the effects are restricted to the injection site. Microneedle arrays may represent a better way to deliver siRNAs across the stratum corneum. In this study, we evaluated for the first time the ability of the solid silicon microneedle array for punching holes to deliver cholesterol-modified housekeeping gene (Gapdh) siRNA to the mouse ear skin. Treating the ear with microneedles showed permeation of siRNA in the skin and could reduce Gapdh gene expression up to 66% in the skin without accumulation in the major organs. The results showed that microneedle arrays could effectively deliver siRNA to relevant regions of the skin noninvasively.

Electrotransfer of Plasmid DNA Encoding an Anti-Mouse Endoglin (CD105) shRNA to B16 Melanoma Tumors with Low and High Metastatic Potential Results in Pronounced Anti-Tumor Effects

Endoglin overexpression is associated with highly proliferative tumor endothelium and also with some tumors, including melanoma. Its targeting has anti-tumor effectiveness, which can also be obtained by RNA interference. The aim of our study was to explore the anti-tumor effectiveness of endoglin silencing by electrotransfer of plasmid DNA encoding short hairpin RNA against endoglin in two murine B16 melanoma variants with different metastatic potential on cells, spheroids and subcutaneous tumors in mice. The results demonstrate that endoglin silencing with gene electrotransfer reduces the proliferation, survival and migration of melanoma cells and also has anti-tumor effectiveness, as the therapy resulted in a high percentage of tumor cures (23% and 58% on B16F1 and B16F10 tumors, respectively). The effectiveness of the therapy correlated with endoglin expression in melanoma cells; in vitro the effects were more pronounced in B16F1 cells, which express more endoglin than B16F10. However, the opposite was observed in vivo in tumors, where there was a higher expression of endoglin and better anti-tumor effectiveness in the B16F10 tumor. In conclusion, targeting endoglin for the treatment of melanoma seems to be a concept worthy of further exploration due to the increased therapeutic effect of the therapy based on simultaneous vascular targeting and its direct effect on tumor cells.

Microphthalmia-associated transcription factor in melanoma development and MAP-kinase pathway targeted therapy

Malignant melanoma is a neoplasm of melanocytes, and the microphthalmia-associated transcription factor (MITF) is essential for the existence of melanocytes. MITF's relevance for this cell lineage is maintained in melanoma, where it is an important regulator of survival and balances melanoma cell proliferation with terminal differentiation (pigmentation). The MITF gene is amplified in ~20% of melanomas and MITF mutation can predispose to melanoma development. Furthermore, the regulation of MITF expression and function is strongly linked to the BRAF/MEK/ERK/MAP-kinase (MAPK) pathway, which is deregulated in >90% of melanomas and central target of current therapies. MITF expression in melanoma is heterogeneous, and recent findings highlight the relevance of this heterogeneity for the response of melanoma to MAPK pathway targeting drugs, as well as for MITF's role in melanoma progression. This review aims to provide an updated overview on the regulation of MITF function and plasticity in melanoma with a focus on its link to MAPK signaling.

Short-interference RNAs: becoming medicines

RNA interference is a cellular mechanism by which small molecules of double stranded RNA modulate gene expression acting on the concentration and/or availability of a given messenger RNA. Almost 10 years after Fire and Mello received the Nobel Prize for the discovery of this mechanism in flat worms, RNA interference is on the edge of becoming a new class of therapeutics. With various phase III studies underway, the following years will determine whether RNAi-therapeutics can rise up to the challenge and become mainstream medicines. The present review gives a thorough overview of the current status of this technology focusing on the path to the clinic of this new class of compounds.

siRNA delivery via electropulsation: a review of the basic processes

Due to their capacity for inducing strong and sequence specific gene silencing in cells, small interfering RNAs (siRNAs) are now recognized not only as powerful experimental tools for basic research in Molecular biology but with promising potentials in therapeutic development. Delivery is a bottleneck in many studies. There is a common opinion that full potential of siRNA as therapeutic agent will not be attained until better methodologies for its targeted intracellular delivery to cells and tissues are developed. Electropulsation (EP) is one of the physical methods successfully used to transfer siRNA into living cells in vitro and in vivo. This review will describe how siRNA electrotransfer obeys characterized biophysical processes (cell-size-dependent electropermeabilization, electrophoretic drag) with a strong control of a low loss of viability. Protocols can be easily adjusted by a proper setting of the electrical parameters and pulsing buffers. EP can be easily directly applied on animals. Preclinical studies showed that electropermeabilization brings a direct cytoplasmic distribution of siRNA and an efficient silencing of the targeted protein expression. EP appears as a promising tool for clinical applications of gene silencing. A panel of successful trials will be given.

Acid sphingomyelinase determines melanoma progression and metastatic behaviour via the microphtalmia-associated transcription factor signalling pathway

Melanoma is a rapidly growing and highly metastatic cancer with high mortality rates, for which a resolutive treatment is lacking. Identification of novel therapeutic strategies and biomarkers of tumour stage is thus of particular relevance. We report here on a novel biomarker and possible candidate therapeutic target, the sphingolipid metabolising enzyme acid sphingomyelinase (A-SMase). A-SMase expression correlates inversely with tumour stage in human melanoma biopsies. Studies in a mouse model of melanoma and on cell lines derived from mouse and human melanomas demonstrated that A-SMase levels of expression actually determine the malignant phenotype of melanoma cells in terms of pigmentation, tumour progression, invasiveness and metastatic ability. The action of A-SMase is mediated by the activation of the extracellular signal-regulated kinase, the subsequent proteasomal degradation of the Microphtalmia-associated transcription factor (Mitf) and inhibition of cyclin-dependent kinase 2, Bcl-2 and c-Met, downstream targets of Mitf involved in tumour cell proliferation, survival and metastatisation.

Gene Silencing in Skin After Deposition of Self-Delivery siRNA With a Motorized Microneedle Array Device

Despite the development of potent siRNAs that effectively target genes responsible for skin disorders, translation to the clinic has been hampered by inefficient delivery through the stratum corneum barrier and into the live cells of the epidermis. Although hypodermic needles can be used to transport siRNA through the stratum corneum, this approach is limited by pain caused by the injection and the small volume of tissue that can be accessed by each injection. The use of microneedle arrays is a less painful method for siRNA delivery, but restricted payload capacity limits this approach to highly potent molecules. To address these challenges, a commercially available motorized microneedle array skin delivery device was evaluated. This device combines the positive elements of both hypodermic needles and microneedle array technologies with little or no pain to the patient. Application of fluorescently tagged self-delivery (sd)-siRNA to both human and murine skin resulted in distribution throughout the treated skin. In addition, efficient silencing (78% average reduction) of reporter gene expression was achieved in a transgenic fluorescent reporter mouse skin model. These results indicate that this device effectively delivers functional sd-siRNA with an efficiency that predicts successful clinical translation.

Delivery of RNAi-Based Oligonucleotides by Electropermeabilization

For more than a decade, understanding of RNA interference (RNAi) has been a growing field of interest. The potent gene silencing ability that small oligonucleotides have offers new perspectives for cancer therapeutics. One of the present limits is that many biological barriers exist for their efficient delivery into target cells or tissues. Electropermeabilization (EP) is one of the physical methods successfully used to transfer small oligonucleotides into cells or tissues. EP consists in the direct application of calibrated electric pulses to cells or tissues that transiently permeabilize the plasma membranes, allowing efficient in vitro and in vivo cytoplasmic delivery of exogenous molecules. The present review reports on the type of therapeutic RNAi-based oligonucleotides that can be electrotransferred, the mechanism(s) of their electrotransfer and the technical settings for pre-clinical purposes.

Gene silencing following siRNA delivery to skin via coated steel microneedles: In vitro and in vivo proof-of-concept

The development of siRNA-based gene silencing therapies has significant potential for effectively treating debilitating genetic, hyper-proliferative or malignant skin conditions caused by aberrant gene expression. To be efficacious and widely accepted by physicians and patients, therapeutic siRNAs must access the viable skin layers in a stable and functional form, preferably without painful administration. In this study we explore the use of minimally-invasive steel microneedle devices to effectively deliver siRNA into skin. A simple, yet precise microneedle coating method permitted reproducible loading of siRNA onto individual microneedles. Following recovery from the microneedle surface, lamin A/C siRNA retained full activity, as demonstrated by significant reduction in lamin A/C mRNA levels and reduced lamin A/C protein in HaCaT keratinocyte cells. However, lamin A/C siRNA pre-complexed with a commercial lipid-based transfection reagent (siRNA lipoplex) was less functional following microneedle coating. As Accell-modified "self-delivery" siRNA targeted against CD44 also retained functionality after microneedle coating, this form of siRNA was used in subsequent in vivo studies, where gene silencing was determined in a transgenic reporter mouse skin model. Self-delivery siRNA targeting the reporter (luciferase/GFP) gene was coated onto microneedles and delivered to mouse footpad. Quantification of reporter mRNA and intravital imaging of reporter expression in the outer skin layers confirmed functional in vivo gene silencing following microneedle delivery of siRNA. The use of coated metal microneedles represents a new, simple, minimally-invasive, patient-friendly and potentially self-administrable method for the delivery of therapeutic nucleic acids to the skin.

Myostatin acts as an autocrine/paracrine negative regulator in myoblast differentiation from human induced pluripotent stem cells

Myostatin, also known as growth differentiation factor (GDF-8), regulates proliferation of muscle satellite cells, and suppresses differentiation of myoblasts into myotubes via down-regulation of key myogenic differentiation factors including MyoD. Recent advances in stem cell biology have enabled generation of myoblasts from pluripotent stem cells, but it remains to be clarified whether myostatin is also involved in regulation of artificial differentiation of myoblasts from pluripotent stem cells. Here we show that the human induced pluripotent stem (iPS) cell-derived cells that were induced to differentiate into myoblasts expressed myostatin and its receptor during the differentiation. An addition of recombinant human myostatin (rhMyostatin) suppressed induction of MyoD and Myo5a, resulting in significant suppression of myoblast differentiation. The rhMyostatin treatment also inhibited proliferation of the cells at a later phase of differentiation. RNAi-mediated silencing of myostatin promoted differentiation of human iPS-derived embryoid body (EB) cells into myoblasts. These results strongly suggest that myostatin plays an important role in regulation of myoblast differentiation from iPS cells of human origin. The present findings also have significant implications for potential regenerative medicine for muscular diseases.

Kinesin spindle protein SiRNA slows tumor progression

The kinesin spindle protein (KSP), a member of the kinesin superfamily of microtubule-based motors, plays a critical role in mitosis as it mediates centrosome separation and bipolar spindle assembly and maintenance. Inhibition of KSP function leads to cell cycle arrest at mitosis with the formation of monoastral microtubule arrays, and ultimately, to cell death. Several KSP inhibitors are currently being studied in clinical trials and provide new opportunities for the development of novel anticancer therapeutics. RNA interference (RNAi) may represent a powerful strategy to interfere with key molecular pathways involved in cancer. In this study, we have established an efficient method for intratumoral delivery of siRNA. We evaluated short interfering RNA (siRNA) duplexes targeting luciferase as surrogate marker or KSP sequence. To examine the potential feasibility of RNAi therapy, the siRNA was transfected into pre-established lesions by means of intratumor electro-transfer of RNA therapeutics (IERT). This technology allowed cell permeation of the nucleic acids and to efficiently knock down gene expression, albeit transiently. The KSP-specific siRNA drastically reduced outgrowth of subcutaneous melanoma and ovarian cancer lesions. Our results show that intratumoral electro-transfer of siRNA is feasible and KSP-specific siRNA may provide a novel strategy for therapeutic intervention.

Progress toward in vivo use of siRNAs-II

RNA interference (RNAi) has been extensively employed for in vivo research since its use was first demonstrated in mammalian cells 10 years ago. Design rules have improved, and it is now routinely possible to obtain reagents that suppress expression of any gene desired. At the same time, increased understanding of the molecular basis of unwanted side effects has led to the development of chemical modification strategies that mitigate these concerns. Delivery remains the single greatest hurdle to widespread adoption of in vivo RNAi methods. However, exciting advances have been made and new delivery systems under development may help to overcome these barriers. This review discusses advances in RNAi biochemistry and biology that impact in vivo use and provides an overview of select publications that demonstrate interesting applications of these principles. Emphasis is placed on work with synthetic, small interfering RNAs (siRNAs) published since the first installment of this review which appeared in 2006.

Preclinical development of siRNA therapeutics for AL amyloidosis

Amyloid light chain (AL) amyloidosis is a rare hematologic disorder characterized by the accumulation of a misfolded monoclonal immunoglobulin (Ig) light chain (LC) as fibrillar protein deposits. Current treatments, including cytotoxic chemotherapy and immunomodulatory therapy, are directed at killing the plasma cells that produce the LCs, but have significant toxicity for other cell types. We have designed small interfering RNAs (siRNAs) targeting the amyloidogenic LC messenger RNA (mRNA) in order to reduce expression of the amyloid precursor protein. Using nanomolar concentrations of siRNAs, we have inhibited synthesis of LC in transfected cells in vitro in a dose-dependent fashion. Furthermore, in an in vivo plasmacytoma mouse model of AL amyloidosis, we have demonstrated that these siRNAs can significantly reduce local production and circulating levels of LC. This model system highlights the therapeutic potential of siRNA for AL amyloidosis.

Comparison of the antimelanogenic effects of p-coumaric acid and its methyl ester and their skin permeabilities

BACKGROUND

p-Coumaric acid (PCA) inhibits human tyrosinase (TYR) activity and melanin synthesis in human epidermal melanocytes.

OBJECTIVE

The purpose of the current study was to examine the potential of PCA and its hydrophobic derivative, methyl p-coumarate (MPC), as hypopigmenting agents for topical use.

METHODS

PCA and MPC were comparatively tested against in vitro human TYR enzyme activity and cellular melanin synthesis in human epidermal melanocytes. Permeation studies were undertaken using an artificial lipophilic membrane and an excised porcine skin. In vivo hypopigmenting efficacy was assessed on the skin of melanin-possessing hairless mice exposed to UVB.

RESULTS

Although PCA was a stronger inhibitor than MPC against TYR activity in vitro, the former inhibited cellular melanin synthesis less effectively than the latter. A non-cell based permeability assay indicated that PCA was practically impermeable through the lipophilic barrier while MPC was highly permeable. In contrast, an ex vivo skin permeation study demonstrated that topically applied PCA in the form of a cream can diffuse into the aqueous medium underneath the skin. No MPC was released from a MPC cream but PCA was released instead as a bio-converted product. Topical application of PCA cream attenuated the UVB-induced erythema formation and pigmentation in mice models, more effectively compared with MPC cream.

CONCLUSION

PCA may be useful as an active ingredient for topical applications for a hypopigmenting effect. MPC has potential as a hypopigmenting agent but requires rather invasive methods for its delivery to the target cells.

Noninvasive and efficient transdermal delivery of CpG-oligodeoxynucleotide for cancer immunotherapy

Oligodeoxynucleotides containing unmethylated cytosine-phosphate-guanosine motifs (CpG-ODN) possess immunostimulatory effects and potential antitumor activity. Since the skin is an easily available site of administration of CpG-ODN due to its accessibility and the presence of abundant antigen presenting cells, it is expected that the application of CpG-ODN to the skin would induce systemic immune response and antitumor activity. However, it is difficult to deliver hydrophilic macromolecules including CpG-ODN through the skin. We have previously demonstrated that small interfering RNA (siRNA) was efficiently delivered into rat epidermis by iontophoresis. In this report, we investigate the effect of transdermal iontophoretic delivery of CpG-ODN on the induction of immune responses and antitumor activity against B16F1 melanoma in mice. Iontophoresis promoted CpG-ODN delivery into the epidermis and dermis. Furthermore, iontophoretic delivery of CpG-ODN to the skin induced the expression of proinflammatory and Th1-type cytokines in the skin and draining lymph node. Finally, transdermal iontophoretic delivery of CpG-ODN led to antitumor activity against B16F1 melanoma. Interestingly, the CpG-ODN administration site is not restricted to the tumor area. In conclusion, CpG-ODN delivered transdermally induced potent antitumor activity, and our system is expected to serve as a simple and noninvasive approach for cancer immunotherapy.

Prognostic value of microphthalmia-associated transcription factor and tyrosinase as markers for circulating tumor cells detection in patients with melanoma

The aim of this study was to analyze microphthalmia-associated transcription factor (MITF) as a marker for the detection of circulating melanoma cells, determine its prognostic value in melanoma patients, and compare it with tyrosinase. Blood samples from 201 melanoma patients in all stages of the disease and 40 healthy volunteers were analyzed. RNA was isolated from mononuclear cell fraction of the blood and assayed by reverse transcription-PCR for the expression of MITF and tyrosinase. All samples from healthy volunteers were negative for both MITF and tyrosinase. Out of 201 blood samples from melanoma patients 32 were positive for MITF, 20 for tyrosinase, and four for both MITF and tyrosinase. Analysis of MITF as an additional marker to tyrosinase allowed for detection of circulating melanoma cells in a larger number of melanoma patients in comparison to tyrosinase analysis alone (48 vs. 20 positive). A positive value of MITF was associated with shorter progression-free (P=0.005) and overall survival (P=0.042). A positive value of tyrosinase was associated with shorter overall survival (P=0.012), whereas there was no significant association between the value of tyrosinase and progression-free survival. The value of MITF was selected with multivariate analysis as the independent prognostic factor for progression-free survival, whereas the only independent prognostic factor for overall survival was the stage of disease. This study has shown that MITF is a specific marker for detection of circulating melanoma cells that has a prognostic value in melanoma patients. Determination of MITF in addition to tyrosinase improved the detection of circulating melanoma cells in melanoma patients.

Bioelectric applications for treatment of melanoma

Two new cancer therapies apply bioelectric principles. These methods target tumor structures locally and function by applying millisecond electric fields to deliver plasmid DNA encoding cytokines using electrogene transfer (EGT) or by applying rapid rise-time nanosecond pulsed electric fields (nsPEFs). EGT has been used to locally deliver cytokines such as IL-12 to activate an immune response, resulting in bystander effects. NsPEFs locally induce apoptosis-like effects and affect vascular networks, both promoting tumor demise and restoration of normal vascular homeostasis. EGT with IL-12 is in melanoma clinical trials and nsPEFs are used in models with B16F10 melanoma in vitro and in mice. Applications of bioelectrics, using conventional electroporation and extensions of it, provide effective alternative therapies for melanoma.

Regulation of cytokines by small RNAs during skin inflammation

Intercellular signaling by cytokines is a vital feature of the innate immune system. In skin, an inflammatory response is mediated by cytokines and an entwined network of cellular communication between T-cells and epidermal keratinocytes. Dysregulated cytokine production, orchestrated by activated T-cells homing to the skin, is believed to be the main cause of psoriasis, a common inflammatory skin disorder. Cytokines are heavily regulated at the transcriptional level, but emerging evidence suggests that regulatory mechanisms that operate after transcription play a key role in balancing the production of cytokines. Herein, we review the nature of cytokine signaling in psoriasis with particular emphasis on regulation by mRNA destabilizing elements and the potential targeting of cytokine-encoding mRNAs by miRNAs. The proposed linkage between mRNA decay mediated by AU-rich elements and miRNA association is described and discussed as a possible general feature of cytokine regulation in skin. Moreover, we describe the latest attempts to therapeutically target cytokines at the RNA level in psoriasis by exploiting the cellular RNA interference machinery. The applicability of cytokine-encoding mRNAs as future clinical drug targets is evaluated, and advances and obstacles related to topical administration of RNA-based drugs targeting the cytokine circuit in psoriasis are described.

MDR1a/1b gene silencing enhances drug sensitivity in rat fibroblast-like synoviocytes

BACKGROUND

Drug resistance mediated by P-glycoprotein (P-gp) is one of the major reasons for the failure of rheumatoid arthritis (RA) therapy with disease modifying anti-rheumatic drugs and glucocorticoids. In the present study, we aimed to investigate the in vitro effectiveness of small interfering RNA (siRNA) to render rat fibroblast-like synoviocytes (FLS) susceptible to drugs. We also attempted the electroporation-mediated transfer of siRNA against multidrug resistance (MDR) genes into rat knee joints.

METHODS

FLS were transfected with siRNAs corresponding to MDR1a and MDR1b genes. FLS were treated with dexamethasone (DEX) and lipopolysaccharide. The mRNA and protein levels of tumor necrosis factor-alpha, interleukin (IL)-6 and IL-1beta were measured. Both siRNAs were co-transduced into rat knee joints by an electroporation method and evaluated the target gene expressions in the synovium.

RESULTS

Each siRNA could sequence-specifically reduce the target gene expression by over 70% and effectively suppressed P-gp expression and function in the FLS. Both gene expression and protein production of the inflammatory cytokines in the cells transfected with siRNA were reduced by a greater amount compared to in control cells. The in vivo electroporation-mediated transduction of siRNA could significantly inhibit the target gene expressions.

CONCLUSIONS

MDR1a/1b gene silencing by siRNA could effectively inhibit P-gp in rat FLS, resulting in a significant enhancement of the anti-inflammatory effects of DEX. The in vivo siRNA transduction could successfully silence MDR gene expression in the rat synovium. These findings indicate that the siRNA targeting MDR gene could be a useful tool for treating refractory arthritis in RA.

Cutaneous short-interfering RNA therapy

Since the 1990s, RNA interference (RNAi) has become a major subject of interest, not only as a tool for biological research, but also, more importantly, as a therapeutic approach for gene-related diseases. The use of short-interfering RNAs (siRNAs) for the sequence-specific knockdown of disease-causing genes has led to numerous preclinical and even a few clinical studies. Applications for cutaneous delivery of therapeutic siRNA are now emerging owing to a strong demand for effective treatments of various cutaneous disorders. Although successful studies have been performed using several different delivery techniques, most of these techniques encounter limitations for translation to the clinic with regards to patient compliance. This review describes the principal findings and applications in cutaneous RNAi therapy and focuses on the promises and pitfalls of the delivery systems.

MicroRNAs targeting mutant K-ras by electrotransfer inhibit human colorectal adenocarcinoma cell growth in vitro and in vivo

Mutations of K-ras have been found in 30-60% of colorectal carcinomas and are believed to be associated with tumor initiation, tumor progression and metastasis formation. Therefore, silencing of mutant K-ras expression has become an attractive therapeutic strategy for colorectal cancer treatment. The aim of our study was to investigate the effect of microRNA (miRNA) molecules directed against K-ras (miRNA-K-ras) on K-ras expression level and the growth of colorectal carcinoma cell line LoVo in vitro and in vivo. In addition, we evaluated electroporation as a gene delivery method for transfection of LoVo cells and tumors with plasmid DNA encoding miRNA-K-ras (pmiRNA-K-ras). Results of our study indicated that miRNAs targeting K-ras efficiently reduced K-ras expression and cell survival after in vitro electrotransfection of LoVo cells with pmiRNA-K-ras. In vivo, electroporation has proven to be a simple and efficient delivery method for local administration of pmiRNA-K-ras molecules into LoVo tumors. This therapy shows pronounced antitumor effectiveness and has no side effects. The obtained results demonstrate that electrogene therapy with miRNA-K-ras molecules can be potential therapeutic strategy for treatment of colorectal cancers harboring K-ras mutations.

Mitf silencing cooperates with IL-12 gene transfer to inhibit melanoma in mice

Malignant melanoma is a malignant neoplasm originating from the melanocyte lineage. Microphthalmia-associated transcription factor (Mitf) is crucially involved in the melanin synthesis as well as proliferation and survival of melanocyte and melanoma. We previously showed that short interfering RNA (siRNA) that is specific for the Mitf gene (Mitf-siRNA) significantly inhibited growth of B16 melanoma after electro-transfected in vivo into preestablished tumor in mice. Here we assessed efficacy of electroporation-mediated co-transfection of Mitf-siRNA and IL-12 gene in the treatment of murine melanoma. As results, the tumor growth was more strongly inhibited by intratumor co-transfection with Mitf-siRNA and IL-12-encoding plasmid DNA than by transfection with either of the molecules alone. The co-transfection induced intratumor infiltration of CD4+ and CD8+ T cells, and hampered neoangiogenesis in the tumor. The findings suggest that the RNAi/cytokine gene combination therapy by means of electroporation may become a novel and efficacious therapeutic modality to treat neoplasms including melanoma.

Simultaneous suppression of MITF and BRAF V600E enhanced inhibition of melanoma cell proliferation

Microphthalmia-associated transcription factor (MITF) is a master gene regulating differentiation of melanocytes, and a lineage survival oncogene mediating pro-proliferative function in malignant melanoma. However, high expression of MITF also has an anti-proliferative effect. To clarify the therapeutic implication of MITF as a molecular target for human melanoma, we evaluated the role of MITF in cell proliferation in a panel of human melanoma cell lines which express different levels of MITF. We found that both MITF depletion and forced expression of MITF significantly inhibited proliferation, suggesting that endogenous MITF is regulated at an appropriate level for melanoma cell proliferation, and could be a molecular target for melanoma. However, half of the melanoma cell lines in this study were relatively resistant to MITF depletion, indicating other treatment strategies are required for therapy. Our microarray analysis indicated that regulation of several cell growth-associated molecules may be independent of MITF and dependent on BRAF(V600E). Thus to enhance the anti-proliferative effect of MITF down-regulation, we combined shRNA-mediated MITF depletion with BRAF(V600E) inactivation, another known molecular target for melanoma. Indeed, simultaneous depletion of both MITF and BRAF(V600E) significantly inhibited melanoma growth even for the melanoma cell lines resistant to MITF depletion. These results suggest MITF may be an important molecular target for human melanoma and simultaneous inhibition of MITF and MAPK signaling may be an attractive strategy for melanoma treatment.

Amelioration of psoriasis by anti-TNF-alpha RNAi in the xenograft transplantation model

Tumor necrosis factor-alpha (TNF-alpha) is upregulated in psoriatic skin and represents a prominent target in psoriasis treatment. The level of TNF-alpha-encoding mRNA, however, is not increased in psoriatic skin, and it remains unclear whether intervention strategies based on RNA interference (RNAi) are therapeutically relevant. To test this hypothesis the present study describes first the in vitro functional screening of a panel of short hairpin RNAs (shRNAs) targeting human TNF-alpha mRNA and, next, the transfer of the most potent TNF-alpha shRNA variant, as assessed in vitro, to human skin in the psoriasis xenograft transplantation model by the use of lentiviral vectors. TNF-alpha shRNA treatment leads to amelioration of the psoriasis phentotype in the model, as documented by reduced epidermal thickness, normalization of the skin morphology, and reduced levels of TNF-alpha mRNA as detected in skin biopsies 3 weeks after a single vector injection of lentiviral vectors encoding TNF-alpha shRNA. Our data show efficient lentiviral gene delivery to psoriatic skin and therapeutic applicability of anti-TNF-alpha shRNAs in human skin. These findings validate TNF-alpha mRNA as a target molecule for a potential persistent RNA-based treatment of psoriasis and establish the use of small RNA effectors as a novel platform for target validation in psoriasis and other skin disorders.

Inhibition of melanogenesis by tyrosinase siRNA in human melanocytes

Tyrosinase (TYR) plays a critical role in cellular melanogenesis and, thus, has been the major target of pharmacological approaches for the control of skin pigmentation. This study examined an alternative molecular approach using TYR-small interfering RNA (siRNA) to control melanogenesis in the human melanocytes. Both the mRNA and protein levels of TYR were significantly lowered by TYR-siRNA treatment, whereas TYR-related protein 1 and TYR-related protein 2 displayed no such changes. TYR-siRNA treatment inhibited the cellular melanin synthesis from the externally supplied TYR substrate L-tyrosine. TYR-siRNA also suppressed melanin synthesis and decreased the viability of cells exposed to ultraviolet radiation, supporting a critical role of melanin in protection against ultraviolet radiation. These results suggest that molecular approaches using siRNA targeted to the enzymes of melanogenic pathway may provide a novel strategy for the control of cell pigmentation.

Terminal and progenitor lineage-survival oncogenes as cancer markers

Tumour classification has traditionally focused on differentiation and cellular morphology, and latterly on the application of genomic approaches. By combining chromatin immunoprecipitation with expression array, it has been possible to identify direct gene targets for transcription factors for nuclear hormone receptors. At the same time, there have been great strides in deriving stem and progenitor cells from tissues. It is therefore timely to propose that pairing the isolation of these cell subpopulations from tissues and tumours with these genomics approaches will reveal conserved gene targets for transcription factors. By focusing on transcription factors (lineage-survival oncogenes) with roles in both organogenesis and tumourigenesis at multiple organ sites, we suggest that this comparative genomics approach will enable developmental biology to be used more fully in relation to understanding tumour progression and will reveal new cancer markers. We focus here on neurogenesis and neuroendocrine differentiation in tumours.

Allele-specific silencing of the dominant disease allele in sialuria by RNA interference

Dominant disease alleles are attractive therapeutic targets for allele-specific gene silencing by small interfering RNA (siRNA). Sialuria is a dominant disorder caused by missense mutations in the allosteric site of GNE, coding for the rate-limiting enzyme of sialic acid biosynthesis, UDP-GlcNAc 2-epimerase/ManNAc kinase. The resultant loss of feedback inhibition of GNE-epimerase activity by CMP-sialic acid causes excessive production of free sialic acid. For this study we employed synthetic siRNAs specifically targeting the dominant GNE mutation c.797G>A (p.R266Q) in sialuria fibroblasts. We demonstrated successful siRNA-mediated down-regulation of the mutant allele by allele-specific real-time PCR. Importantly, mutant allele-specific silencing resulted in a significant decrease of free sialic acid, to within the normal range. Feedback inhibition of GNE-epimerase activity by CMP-sialic acid recovered after silencing demonstrating specificity of this effect. These findings indicate that allele-specific silencing of a mutated allele is a viable therapeutic strategy for autosomal dominant diseases, including sialuria.

Microphthalmia-associated transcription factor is a critical transcriptional regulator of melanoma inhibitor of apoptosis in melanomas

Melanoma inhibitor of apoptosis (ML-IAP) is a potent inhibitor of apoptosis, which is highly expressed in melanomas and likely contributes to their resistance to chemotherapeutic treatments. Herein, we show that the lineage survival oncogene microphthalmia-associated transcription factor (MITF) is a critical regulator of ML-IAP transcription in melanoma cells. The ML-IAP promoter contains two MITF consensus sites, and analysis of MITF and ML-IAP mRNA levels revealed a high correlation in melanoma tumor samples and cell lines. In reporter assays, MITF promoted a strong stimulation of transcriptional activity from the ML-IAP promoter, and MITF bound the endogenous ML-IAP promoter in melanoma cells by chromatin immunoprecipitation and electrophoretic mobility shift assay. Strikingly, small interfering RNA (siRNA)-mediated knockdown of MITF in melanoma cells led to a dramatic decrease in ML-IAP mRNA and protein levels, establishing that ML-IAP expression in melanoma cells is MITF dependent. Additionally, cyclic AMP-mediated induction of MITF expression in melanocytes resulted in increased ML-IAP expression, suggesting that melanocytes can express ML-IAP when MITF levels are heightened. Disruption of MITF by siRNA led to a decrease in melanoma cell viability, which could be rescued by ectopic expression of ML-IAP. Collectively, these findings implicate MITF as a major transcriptional regulator of ML-IAP expression in melanomas, and suggest that ML-IAP contributes to the prosurvival activity of MITF in melanoma progression.

Nonviral approaches for targeted delivery of plasmid DNA and oligonucleotide

Successful gene therapy depends on the development of efficient delivery systems. Although pDNA and ODN are novel candidates for nonviral gene therapy, their clinical applications are generally limited owing to their rapid degradation by nucleases in serum and rapid clearance. A great deal of effort had been devoted to developing gene delivery systems, including physical methods and carrier-mediated methods. Both methods could improve transfection efficacy and achieve high gene expression in vitro and in vivo. As for carrier-mediated delivery in vivo, since gene expression depends on the particle size, charge ratio, and interaction with blood components, these factors must be optimized. Furthermore, a lack of cell-selectivity limits the wide application to gene therapy; therefore, the use of ligand-modified carriers is a promising strategy to achieve well-controlled gene expression in target cells. In this review, we will focus on the in vivo targeted delivery of pDNA and ODN using nonviral carriers.

Nucleofection is a highly effective gene transfer technique for human melanoma cell lines

Despite the increasing use of gene transfer strategies in the study of cellular and molecular biology, melanoma cells have remained difficult to transfect in a safe, efficient, and reproducible manner. In the present study, we report the successful use of nucleofector technology to transfect human melanoma cell lines. This technology uses an empirically derived combination of cell line-specific solutions and nucleofector programmes to electroporate nucleic acid substrates directly into the cell nucleus. Using a colorimetric beta-galactosidase assay, we optimized nucleofection parameters for 13 melanoma cell lines, leading to maximum transfection efficiency and cell survival. The combinations of cell solutions NHEM or T and nucleofector programmes A-24 or U-20 produced the best results. We compared nucleofection with two commercially available lipid-based gene transfer systems, effectene and lipofectamine 2000 using a green fluorescent protein reporter vector. Nucleofection demonstrated a 3- to 40-fold improvement in transfection efficiency when compared with the lipid-based counterparts. Nucleofection was also superior in transfecting small-interfering RNA (siRNA) as determined by Western blot analysis. Lastly, we applied nucleofection to the simultaneous transfection of a p53-dependent luciferase plasmid and p53-siRNA. Experiments using dual transfection showed knockdown of p53 expression and silencing of the reporter plasmid. In conclusion, nucleofection is highly effective for the transfer of nucleic acid substrates, singly or in combination, into human melanoma cell lines.

Genetics of melanoma tumorigenesis

Melanoma therapy is moving away from combinatorial approaches and towards newer targeted strategies. With the identification of mutations in various RAS pathway genes, there are now tremendous opportunities to bring inhibitors of RAS signalling to the clinical arena.

In vivo gene silencing in solid tumors by targeted electrically mediated siRNA delivery

RNA interference (RNAi)-mediated gene silencing approaches appear very promising for therapies based on the targeted inhibition of disease-relevant genes. The major hurdle to the therapeutic development of RNAi strategies remains, however, the efficient delivery of the RNAi-inducing molecules, the short interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs), to the target tissue. With respect to cancer treatment the development of efficient delivery methods into solid tumors appears as a critical issue. However, very few studies have addressed this problem. In this study we have investigated the contribution of electrically mediated delivery of siRNA into murine tumors stably expressing an enhanced green fluorescent protein (EGFP) target reporter gene. The silencing of EGFP gene expression was quantified over time by fluorescence imaging in the living animal. Our study indicates that electric field can be used as an efficient method for siRNA delivery and associated gene silencing into cells of solid tumors in vivo.